54 THi: AVHITK PINE. 



■natter, as much sunlight as the i)laiits will iMulure witliout wiltinf;, a fairly low temperature, and 

 an abundant supijly of fresh air. Mr. .1. Dawson, of the Arnold Arboretum, suggests watering 

 the young plants from below, so as to avoid wilting the leaves, as a means of i)rev«'ntion. Other 

 suggestions will l)e found in recent literature of the subject, practically in the re])orts of various 

 agricultural exiteriment stations.' 



A disease which attacks the trunk of the tree, at various ages, is very prevalent in pine 

 forests, and occasions the condition known among luinbcrmf^ii as ''i)unky jiine." A diseased tree 

 can freipieiitly be lecogni/.ed by its ha\ing one or more knots with a rough, irregular contour, at 

 a considerable height above the ground, commonly conspicuous by a considerable outllow of resin. 

 These seem to result from the brc^aking olf of branches, followed by gradual decay at the jdace 

 where they have separated from the tree, in such a way as to admit water into the trunk, the 

 oi»eniug being afterwards partially covered by subsetjuent growth of the tree while decay is going 

 ou inside. 



Upon examining the wood of such a tree, it is seen te be discolored and in various stages of 

 decay, the diseased condition extending inward from the knot hole, and both upward and 

 downward from it in the trunk. Hy inspecting logs cut from such trees, it will be noticed that 

 the decayed i)ortion may have tilled up the center, making a rotten heart: or it may follow the 

 rings of growth for some distance, midway from the center to the periidiery; or it may be still 

 nearer to the surface, its jiosition and extent being very variable and following no recognizable 

 rule. The parts diseased are utterly worthless, though boards containing a greater or less amount 

 of wood thus affected are (tommon in the market. Mi(;roscoi)ic examination shows that the wood 

 is penetrated by the tilaments of a fungus, and that the elements of which the wood is made up 

 have been greatly altered, and to a considerable extent decomposed by its action. 



(joutinui'd observation in the jiine woods of Michigan, in ditlercnt years, does not so far Justify 

 the reference of this disease to any single s])ecies of the various fungi found growing upon the 

 trunks and logs of decaying pine trees. But whatever the species, one or several, concerned in 

 jnodncing or hastening the condition described, the general facts, as stated above, api)ear to be 

 that the disease finds its way where the separation and decay of a branch i)resent8 a favorable 

 jdace for the entrance of water and the spores of fungi, and that it 8i)rea<ls so extensively in the 

 trunk as to entirely ruin large and valuable trees. 



In our natural forests there is, of course, neither remedy nor i>revention,but in artificial culti- 

 vation careful and seasonable pruning would doubtless be the most effectual preventive, since, if 

 ltro])erly i>erformed, the wounds left by the removal of branches would soon be grown over and 

 there would be no further tlanger from this source. 



I'.XI'I.AXATION OF I'LATK XII. 



1. Agaricim vieJleus, clnflter of yoviiig 8pori>pliore8. 



S. AgariiiiH mtUeuK, larger HpiiiDplioro with root-like orjjan of attachnioiit. 



.?. l^oot of spriicr tren invadrd by mycelium of Aijaricus vtelli-tin; rluzoniorph of Hrinir fiiii^iiK on tlie riglit. 



4-0, rrai;iMfiiits of jiiiie wood sliowiii;; the ilrstriictive action of .li/ariciiK mellenii. 



7. .Stunij) of White I'ine attaiked l>y I'ohjiiiirun axnonun : the lieart is still sound, luit is Hinronmled l>y ileeayed 



wood and spots lilleil with masses of rosin. 

 ■S\ Wood of NiirwMV Si>rn(0 in early stages of decay occasioned by action of I'olypornt nnnoxiix; th« white areas 



liave become delignilled, anil tlie wood elements eotniiosiiif; tliem are soft and easily separable. 

 !). Wood elements of Norway Spruce isolated .and showing the mycelium of the I'ohjporuK annosun. 

 10. Fruiting liyplne and spores of I'lili/jionis annosiia. 



KXI'LANATION OK I'l.ATK XIII. 



J. iStump of Norway Spruce, with a sporojdiori' of I'ohiporiin tinnomis several years old; tlie inner jiortions of the 

 stumii wholly decayed. 



2. Roots of a diseased spruce tree, with numeidus small si)oropliores of roli/ponm annomm attached. 



3. Stuni]> anil part of root system of a young ])inc trio killed l>y the action of Poli/pornn annosiio, the sporophorcs of 



which have grown entirely around the b-ase of the trunk. 

 •/. Mature sporii|iliore of J'tili/puriix ainionim seen from below, showing the porous spore-bearing surface. 

 /i. Mature spiiriiphore of I'olyporiiK annonuii frniii above, showing' the velvety upper surface and concentric bands. 

 C. Mature sjim-ophnro of roJf/pni-iix aiiinmiis in section. 

 7. Modi' of infection; whore the smaller diseased root crosses the larger one, the myceliiini of the I'olyporus annomis 



has penetrated the latter and spread in both ilircetions for some dist.aiice. 



' Cf. Atkinson, Cornell Univ., Agr. Exp. Sta. Bull. 94, 1895. 



